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Old January 11th, 2011, 14:26
fyrfytr1717 fyrfytr1717 is offline
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Join Date: Jul 2008
Location: Turlock, CA
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Re: Radiator Fan Override Switch (The Easy Way)

Hey Mudderoy, been awhile since I've seen you post up here. I imagine XJTalk takes up a majority of your forum time these days. I appreciate your taking the time to provide some feedback. Anyways, I was reading your version of my write up that you linked to in your post and had a couple questions.

I saw that your work around was hooking the relay coil up directly to the battery instead of using the DB/WT wire that I recommended. That should work too as you just need a 12V+ source to make the relay work, but my reason for using the DB/WT is that it is an ignition switched 12V+ source. If you have it hooked up to the battery instead, you could potentially forget to turn the override switch off and cause your battery to drain when you shut the vehicle off. Granted a relay coil doesn't draw much power, but the fact is that the relay coil would remain energized and it would be a small power draw that would eventually leave you with a dead battery. If you don't want to use the DB/WT wire, I'd suggest finding another source of ignition switched power or setting up an ignition switched bus bar for accessories that you don't want to accidentally leave on when the ignition is shut off.

Second, you recommended installing a 10 amp fuse between the switch and the ground. Why? A relay only draws about 0.16 amps so a 10 amp fuse would do very little for you. Additionally placing the fuse where you suggested offers no protection to anything except the short piece of wire connecting the fuse to the ground. You are however correct that you should install a fuse when using your suggestion of hooking the relay up directly to the battery, but it should be as close to the battery as possibly and only needs to be a 1 amp fuse to protect the relay and associated wiring. Using the DB/WT wire for relay power takes advantage of the fact that the DB/WT wire is already a fused circuit.

Again, thanks for the feedback. Maybe I'm just missing something and you can clarify for me?
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